Throttle-type control levers for the graduated delivery of power to hand-held tools, especially pneumatic tools, have long been used on certain types of tools where variable speeds and/or power delivery have been desired. Grinders, sanders, nutrunners and screw drivers are examples of these tools. Usually, the throttle extends roughly parallel to the longitudinal axis of the handle, or the body of the tool when the tool is small enough to be held in the hand. In some larger tools, the throttle is mounted on a handle. The operator grips the handle (or tool body) with the ends of one or more fingers on the throttle. By closing or opening his fingers, the operator can provide varying amounts of pneumatic fluid to the motor, thus controlling the operation of the tool. The throttle is biased in a suitable manner, depending on the construction of the tool, to shut off upon release by the operator.
All the above is old in the art. A need for a "lock-out", or safety interlock, to avoid inadvertent actuation of the tool, either by the operator in the act of picking up the tool or by accidental dropping or rolling the tool on to the throttle, has been observed, and the instant invention is one result.